Projecting the Coupled Impact of Sustainable Groundwater Management Laws and Development Planning on Land-use/land-cover Change in California

Abstract:

Water supply sustainability is a critical issue worldwide. Yet in many groundwater dependent regions, increasing water demand from urban growth and agricultural intensification will place increasing pressure on limited groundwater resources, which is likely to be exacerbated by climate change. This is particularly the case for California's Central Coast, a region that is heavily reliant on local groundwater and where groundwater pumping has historically been largely unregulated. In 2014 California experienced a drought of unprecedented severity and groundwater wells failed in many localities statewide. The state subsequently passed the Sustainable Groundwater Management Act (SGMA) in an effort to bring overdrafted groundwater basins into sustainability. SGMA's requirements have the potential to create widespread land use-land change (LULC) change feedbacks between future development and water demand in the region. We created a novel version of LUCAS, a LULC model that estimates water demand and constrains local development within groundwater basins where pumping exceeds the sustainable water supply. The model was parameterized by reviewing and quantifying local water agency policies from each of the 27 basins subject to SGMA requirements. We compare the coupled impacts of water management and land-use planning on local LULC trends and projections for the Central Coast region from 2001-2061. We examine leakage of development from SGMA-regulated groundwater basins to currently unregulated basins. Lastly, we compare the impact of each policy on estimated groundwater sustainability, conservation of endangered species' critical habitats, prime farmland loss, and disadvantaged communities.